The invention is based on an apparatus for regulating the power consumption of a vacuum cleaner.
It is known to provide, in a vacuum cleaner, an automatic suction power controller (EP 0 379 680 B1) in which the electric motor driving the fan of the vacuum cleaner is activated by a phase-angle control circuit, and its rotation speed and power consumption are influenced so that a vacuum which is substantially constant, or changes only within a predefined bandwidth, is generated in the suction region of the vacuum cleaner.
For this purpose two vacuum switches, usually membrane-controlled, and set to different vacuum response thresholds, are provided and are linked to an activation circuit for the electric motor comprising the phase-angle control circuit in such a way that when both vacuum switches are open, the phase-angle control circuit reacts so as to raise power output; while when both vacuum switches are closed, the electric motor is activated toward lower power consumption, so that when one of the vacuum switches is closed and the other open, the desired power level is achieved and is also substantially maintained by means of the response characteristics of the control circuit to the vacuum switch.
This automatic approximate maintenance of constant power consumption in a vacuum cleaner motor can be supplemented with additional switches which define further, manually adjustable power output modes when actuated by the user.
In a system of this kind for controlling the power consumption of a vacuum cleaner fan motor, problems can result from the circumstance that the line voltage can exhibit fluctuations, which are compensated for by the vacuum switches under automatic control, but in the manually selectable switch positions can lead to considerable differences in output. Such problems can occur even with ordinary fluctuations in line voltage, since the line voltage of a load is squared when incorporated into the power definition; it therefore has a particularly serious effect when different line voltages are used because of national regulations, so that line voltage often fluctuates between 190 and 260 volts in different regions, in some cases additionally complicated by variations in line frequency.
It is possible to define different output data for each regional or national area. This is nevertheless tedious and expensive for the production of electrical appliances in general and vacuum cleaners in particular, so that the underlying object of the invention is to provide a remedy here, and to ensure automatic vacuum cleaner operation regardless of fluctuations in line voltage and frequency, so that even when certain output data are selected manually (for example setting to 300-watt operation or 500-watt operation as a supplement to automatic vacuum regulation, or a "boost" mode), said data are kept constant.